Table 6.

Multivariable analysis for identification of factors associated with radiographic SIJ progression defined as a change in the sacroiliitis sum score over 2 years

Variable	Estimate	95% CI
Prior TNFi use up to the start of X-ray interval yes/no	−0.118	−0.203 to −0.033
Baseline sacroiliac damage (0–7) at start of each X-ray interval	−0.017	−0.041 to 0.207
Female sex	−0.081	−0.170 to 0.007
Symptom duration	0.001	−0.004 to 0.005
Current smoking	0.087	0.001 to 0.173
HLA-B27 negative	0.084	−0.038 to 0.207
NSAID use at start of each X-ray interval	−0.018	−0.112 to 0.077
ASDAS at start of each X-ray interval	0.011	−0.034 to 0.056

Analysis in 302 patients and 483 X-ray intervals (22 events).

ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; CRP, C-reactive protein; HLA-B27, human leucocyte antigen B27; NSAID, non-steroidal anti-inflammatory drug; SIJ, sacroiliac joint; TNFi, tumour necrosis factor inhibitor.